(1) Field of the Invention
The present invention relates to an eyeball locating method and system, particularly to an eyeball locating method and system using an optical sensor for determining the light reflected by the surface of the eyeball.
(2) Description of the Prior Art
Computer makes people's daily life more and more convenient, but for most disabled men, it is rather inconvenient to handle computer.
To help the disabled men to handle computer, several control methods of the man-machine interface system have been developed in the world, such as hand joint control, voice control, electromyogram (EMG) behavior, shoulder control, gassing and so on. The common disadvantage among these control methods is that they are not capable of executing complex control behaviors, and they are also unable to control the computer conveniently and real-timely because the control signal needs complex identification and longer processing period.
To conquer these limits, the technology of using the movement of eyeball to control the computer emerges as the times require. The eyeball tracking system is most common, which is capable of controlling the cursor or keyboard of the computer by detecting the movement of the eyeball in real time. At present, the eyeball tracking system has piezoelectric type, optical type and magnetic type according to the detection principles.
The piezoelectric type is detecting the movement direction of the eyeball by the change of eye pressure, which is pasting the piezoelectric sensor around the eyes, converting the eye pressure into electrical signal by the piezoelectric sensor and measuring the electrical signal. However this system influences the measurement of the electrical signal easily due to sweat.
The magnetic type is measuring the movement of the eyes by forming magnetic field around the eyeball.
The optical type is capturing an eyeball image, coordinating the present target position through algorithm of image analysis, sending the results to the personal computer and driving mouse to execute control instruction.
Refer to FIG. 1 for the head-mounted optical eyeball tracking system 100. The eyeball tracking system 100 has a charge-coupled device (CCD) image detector 120, a screen 140 and a frame 160. The CCD image detector 120 is electrically connected to the screen 140 and disposed on the frame 160 together with the screen 140. When an user 200 wears the frame 160, the CCD image detector 120 and the screen 140 are fixed near the eyes of the user 200 by the frame 160. The screen 140 displays a plurality of the location points (not shown) for the user 200. When the user 200 watches one of the location points on the screen 140, the CCD image detector 120 captures his pupil image and performs binary processing to get the position of the pupil.
Furthermore, the CCD image detector 120 is connected to a computer 180. The CCD image detector 120 collects and analyzes the pupil image real-timely, and converts it into a control order to command the cursor to handle the computer 180.
However, the user 200 of the eyeball tracking system 100 needs to wear the frame 160 to increase success rate. The difficulty of the optical detection is when capturing the pupil image, the contrast ratio between the pupil and the eye white is too low to measure, especially under the condition of glasses obstruct, outer light disturb or eyeball pathological changes. In conclusion, the conventional eyeball tracking system 100 is limited in use and has low resolution, which makes it hard to apply in the view or browsing equipments or general medical occasion.